Telecommunications – Wireless distribution system – Receiver for satellite broadcast
Reexamination Certificate
2002-05-03
2004-03-30
Trost, William (Department: 2683)
Telecommunications
Wireless distribution system
Receiver for satellite broadcast
C455S003020, C455S069000, C455S078000
Reexamination Certificate
active
06714760
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to wireless communication devices and systems, and more specifically, to a wireless device, such as a wireless telephone or modem, capable of communicating with both satellite and terrestrial communication systems.
II. Related Art
There are presently many different types of radiotelephone or wireless communication systems, including different terrestrial based wireless communication systems and different satellite based wireless communication systems. The different terrestrial based wireless systems can include Personal Communications Service (PCS) and cellular systems. Examples of known cellular systems include the cellular Analog Advanced Mobile Phone System (AMPS), and the following digital cellular systems: Code Division Multiple Access (CDMA) systems; Time Division Multiple Access (TDMA) systems; and newer hybrid digital communication systems using both TDMA and CDMA technologies. A CDMA cellular system is described in the Telecommunications Industry Association/Electronic Industries Association (TIA/EIA) Standard IS-95. Combined AMPS & CDMA systems are described in TIA/EIA Standard IS-98. Other communications systems are described in the IMT-2000/UM, or International Mobile Telecommunications System 2000/Universal Mobile Telecommunications System, standards covering what are referred to as wideband CDMA (WCDMA), cdma2000 (such as cdma2000 1× or 3× standards, for example) or TD-SCDMA.
An exemplary CDMA type satellite communication system comprises a constellation of 48 Low Earth Orbit (LEO) satellites and a plurality of ground stations (also referred to as terrestrial fixed stations or gateways). The gateways connect one or more known communication systems and networks to one or more satellite user terminals through the plurality of LEO satellites. Terrestrial based communication systems linked with the gateways can include, for example, telephony ground lines coupled with the Public Switched Telephone Network (PSTN), cellular and PCS systems, dedicated optical or microwave links, or the Internet. The satellite user terminals can be mobile, portable, or fixed terminals, as desired.
Typically, each satellite user terminal can receive and transmit to multiple satellites. This provides a desired level of satellite or spatial diversity. The satellite user terminals use such satellite diversity to improve satellite communication coverage by avoiding blockage of a line-of-site between the satellite user terminal and any given satellite. In some systems, the satellites serve only as frequency translators and repeaters. They may not contain or use specialized signal modulation or demodulation capabilities for changing the signal content, protocols, or structure. A signal transmitted from a user terminal to a satellite is referred to as a satellite uplink signal or frequency. A signal transmitted from the satellite to the user terminal is referred to as a satellite down link signal or frequency. From the perspective of the satellite being a bent-pipe or simple repeater, those signals traversing from the gateway to user terminals are referred to as forward link (communication) signals and those signals traversing from the user terminal to a gateway are referred to as reverse link signals (as viewed from the user terminal perspective).
The satellite converts the satellite uplink frequency (user terminal reverse link) into a gateway-satellite system forward link frequency, transmitted from the satellite to the gateway.
Also, the satellite converts the satellite down link frequency to a satellite system reverse link frequency, transmitted from the satellite to the user terminal (user terminal forward link). For example, if the user terminal down link frequency is 2500 Megahertz (MHz) and its uplink frequency is 1600 MHz, the satellite maps or translates signals at these frequencies to other desired link frequencies, such as 5100 MHz and 6900 MHz, respectively. Each satellite down link or forward link communication signal pattern has a series or set of “beams” (or sectors) illuminating a footprint on the surface of the Earth. A typical satellite might use sixteen such beams. Sometimes multiple beams at different frequencies are used to illuminate the same given area in a single “beam” pattern, with each being referred to as a “sub-beam.”
For CDMA communication systems using Pseudo-Noise (PN) or pseudo-random codes for modulation, each down link beam, and generally each satellite, uses a separate Pseudo-Noise (PN) code phase offset value for purposes of beam identification. Within each beam, orthogonal codes, such as Walsh codes, are used for beam or sub-beam channelization, creating a series of individual code channels for communicating with respect to each user terminal. In practice, the beams from one satellite form a footprint that can cover large geographical regions such as entire countries like the United Sates. The satellites receive the satellite uplink or reverse link communication signals from user terminals also using a series or set of beams (or sectors) in a pattern, typically sixteen. The forward and reverse link beam patterns need not be identical.
In an exemplary CDMA satellite wireless communication system, a common frequency, or set of frequencies defining the different beams, is used by each gateway transmitting to or through the satellites. Common radio frequencies allow simultaneous communication through multiple satellites to or from one gateway. Individual user terminals are separated by the use of lengthy or high chip-rate PN codes on the reverse communication signal link and orthogonal or Walsh Codes (and sub-beams) on the forward communication signal link. The high-rate PN codes and Walsh Codes are used to modulate signals transmitted from gateways and user terminal transceivers. Transmitting terminals (gateway and user terminal) may use different PN codes offset in time from one another (and/or Walsh codes), thereby producing transmitted signals that can be separately received at a receiving terminal.
Each of the gateways transmits a pilot signal having a common PN spreading code or code pair that is offset in code phase from the pilot signal of other gateways. Unique pairs of PN codes can be used to identify satellites within a particular orbital plane. Additionally, each gateway may have a unique identifying PN code and each down link beam (from a satellite to a user terminal) has a different PN code offset with respect to other down link beams for the satellite.
During system operation, a user terminal has a model of the satellite constellation and the user terminal is provided with a list of PN codes and PN code phase offsets for each satellite coming into or within view of the user terminal, or for gateways. Moreover, an outer PN code sequence, as described in U.S. patent application Ser. No. 09/169,358 entitled “
Multi
-
Layered PN Code Spreading In A Multi
-
User Communications System
” by Harms et al, and incorporated herein by reference, can be used to identify specific signal sources such as gateways or satellites.
This PN code can be used to derive a time and phase difference between satellites in view at any time, or having the same and/or different orbits. The user terminal is equipped with elements useful for acquiring and tracking beams from multiple satellites in multiple orbits simultaneously.
CDMA technology provides a mechanism for hand-off between satellite beams by changing PN codes used to demodulate or de-spread the received signals. Generally, this can be accomplished by using one or more codes in a set of codes, and changing the phase of the codes to match different code phase offsets used between different signal sources or beams. When more than one satellite is in view of a user terminal, the user terminal can communicate with the gateway through the more than one satellites. As a result, a call hand-off between satellites can be achieved at the gateway for the user terminal. This ability to communicate with multiple satellites gives the
Ewart James D
Ogrod Gregory D.
Qualcomm Incorporated
Trost William
Wadsworth Philip R.
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